Electronically synchronized sewing machine



W. A. RAMSEY ELECTRONICALLY SYNCHRONIZED SEWING MACHINE June 2, 1970 6 Sheets-Sheet 1 Filed Jan. 8, 1968 9 M F u M INVENTOR WILLARD A. RAMSEY 8V i ATTORNEY OUTPUT H; mm

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ELECTRONICALLY SYNCHRONIZED SEWING MACHINE Filed Jan. 8, 1968 6 Sheets-Sheet 6 FIG I5 INVENTOR WILLARD A. RAMSEY ATTORNEY United States Patent 3,515,080 ELECTRONICALLY SYN CHRONIZED SEWING MACHINE Willard A. Ramsey, Mauldin, S.C., assignor to Her Majesty Industries, Inc., Mauldin, S.C., a corporation of South Carolina Filed Jan. 8, 1968, Ser. No. 696,440 Int. Cl. Dc 5/02 U.S. Cl. 1l2---121.14 Claims ABSTRACT OF THE DISCLOSURE A sewing machine which embodies physically separated needle drive and bobbin drive units which cooperate to produce stitching in a workpiece. Each machine unit embodies its own servo drive means and the drive means are electrically coupled in synchronism so that the units may be operated in unison and moved together in prescribed directions without having any physical connection. A variety of workpiece supporting and feeding means may be employed depending upon the character of the work operation.

CROSS-REFERENCE TO RELATED APPLICATION Reference is made to prior copending application Ser. No. 605,066, filed Dec. 27, 1966, for a self-programmed automatic cornely embroidery system, containing some subject matter common hereto.

BACKGROUND OF THE INVENTION The prior art contains some teachings of sewing machines which are rendered automatic in their operation in whole or in part, generally through the provision of electrical controls and/0r programming devices. In all known cases, however, there remains a physical or mechanical connection between the needle drive of the machine antl the bobbin or looper drive, in order to achieve the precise timing for proper machine operation. Additionally, all sewing machines include an arm support or standard which rises above the work table, through which the mechanical linkage between the needle and bobbin usually extends. This traditional construction definitely limits the open throat area of the machine between the needle and bobbin drives and thereby limits the character of the work and the size of the work which may be accommodated. Therefore, the utility and versatility of conventional sewing machines is necessarily limited and such machines are not completely effective for performing some commercial sewing operations and do not completely adapt themselves to automation. The traditional sewing machine configuration renders it impractical, for example, to control or drive the machine automatically on two right angular axes in one plane while providing controlled rotation about a third axis, such as the needle axis, and this mode of operation is highly desirable in a practical automation system.

The present invention has for its chief aim the overcoming of the deficiencies and inadequacies of the prior art by the provision of a sewing machine which lends itself completely to automation in a self-programmed mode or under external control. In either case, the machine possesses the necessary mobility which has never before been possible to achieve with conventional structures. By means of the invention, the needle and bobbin drive units, while physically separated, and characterized by the absence of any mechanical interconnecting linkages, are caused to operate substantially perfectly in unison and to move in unison in a number of prescribed directions.

SUMMARY OF THE INVENTION The invention sewing machine comprises physically ice separated needle and bobbin drive units, each unit having a support and guiding means and each unit having its own servo drive system. The machine possesses the necessary electrical controls to coordinate and synchronize the operation of the two unit servo drives, whereby the machine units can be driven in unison and in either direction along right angular X and Y axes and rotationally around a third or Z axis which is the needle axis of the machine.

The servo drives of the two basic machine units may include separate motor drives for moving the units in the X and Y axis directions and around the needle axis and each unit is equipped with suitable bearings and slip ring means to allow the necessary electrical signals to pass into and out of the unit while rotation around the needle axis is occurring.

A variety of work supporting and/0r feeding means may be employed with the sewing machine for performing a variety of different work operations. In some cases, the workpiece ma be held stationary at the sewing zone while the machine units are moved relative to the work. In other instances, the work may be shifted in an X axis direction or Y axis direction while th emachine units are controlled along the other coordinate axis and around the needle axis. Great versatility can be achieved in this manner for performing a variety of commercial sewing operations with efficiency.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a partly diagrammatic perspective view of an electronically synchronized sewing machine embodying the invention;

FIG. 2 is a plan view of the sewing machine showing means for controlling or driving it in two right angular directions in a plane;

FIG. 3 is a vertical section taken on line 3-3 of FIG. 2;

FIG. 4 is a vertical section taken on line 4-4 of FIG. 2;

FIG. 5 is a horizontal section on a reduced scale taken on line 55 of FIG. 3;

FIG. 6 is an enlarged fragmentary vertical section taken on line 66 of FIG. 2;

FIG. 7 is a block diagram of electrical circuitry employed to operate the invention in a self-programmed more;

FIG. 8 is an electrical schematic diagram of one form of voltage level converter for the logic circuitry utilized in FIG. 7;

FIG. 9 is an electrical schematic diagram of another form of voltage level converter for the logic circuitry of the invention;

FIG. 10 is a block diagram of an electrical servo system for operating the invention machine under external control as distinguished from self-programmed;

FIG. 11 is a partly diagrammatic vertical cross section through the machine showing one preferred form of work supporting and feeding means utilized in the sewing machine for one class of sewing operation;

FIG. 11a is a plan view of the work feeding and supporting means in FIG. 11;

FIG. 12 is a diagrammatic plan view showing another form of work supporting and feeding means for the sewing machine used for another class of work;

FIG. 13 is a diagrammatic plan view of a further moditied work supporting and feeding means;

FIG. 13a is a side elevational view of the same;

FIG. 14 is a diagrammatic plan view of another form of work supporting and feed means used in connection with another class of work;

FIG. 15 is a diagrammatic perspective view showing the use of the sewing machine in connection with another class of work; and

FIG. 16 is a diagrammatic perspective view of a sewing machine capable of turning on three major axes and also moving along these axes whereby the machine can sew along a compound curve or on a three dimensional form.

DESCRIPTION OF THE PREFERRED EMBODIMENTS Referring to the drawings in which like numerals designate like parts, FIG. 1 illustrates partly diagrammatically the two basic units of the sewing machine, namely, the needle drive unit 20 and the bobbin drive unit 22, disposed in spaced opposing relationship to the needle drive unit on a theoretical Z axis which is the needle axis of the unit 20 and of the machine. It should be thoroughly understood that the units 20 and 22 are physically separated and there is no mechanical linkage or connecting means between them. Therefore, the space between the needle and bobbin units is completely unobstructed in a l directions and this feature is basic to the complete success of the invention. As will be fully described, the machine units 20 and 22 are electrically connected and operated in synchronism and in unison and the two units can be moved bodily in unison around the Z axis or needle axis and may also be shifted in unison in either the plus or minus directions on the X and Y coordinate axes indicated in FIG. 1.

Each unit 20 and 22, FIG. 6, includes a respective rigid mounting portion 24 and 26, and these mounting portions are coupled to unit supporting plates 28 through the medium of thrust bearings 30, preferably of the low friction type which allow ready coaxial rotation of the units 20 and 22 on the Z axis or needle axis.

The needle drive unit 20 comprises above the hearing 30 a main rotary spindle 32 carrying a gear 34. Rotation of this gear 34 imparts rotation to the unit 20 on the needle axis. Attached to the spindle 32 is a sli ring assembly 36 through which a continuous electrical input or output may pass during rotation of the unit 20 around the needle axis. A circumferential step motor 38 having an output gear 40 is also mounted on the plate 28 of unit 20 and the gear 40 meshes with larger gear 34 to drive the latter. An electrical potentiometer 42, designated a sine-cosine potentiometer, is secured to s ip ring assembly 36 and carries a drive gear 44 in mesh with the gear 34.

The needle drive unit 20 includes a sewing needle 46 which reciprocates on the Z axis and may be surrounded by an annular presser foot 48 carrying a small photoelectric cell 50 at one point thereon which constitutes a guiding eye or scanning element for the machine constantly controlling its direction in conjunction with control circuitry, to be described. In substance, the photocell 50 senses the edge of a cloth workpiece and through the circuitry causes the sewing machine to follow the workpiece edge in a proper forward direction. In some instances, the presser foot 48 may be omitted, in which case the photocell 50 is suitably supported on a bracket or the like close to the needle 46 and on the unit 20. The photocell 50 responds to light impinging on it and provides-an electrical signal indicative of the degree of light received and this signal is utilized in the control circuitry.

The bobbin drive unit 22 contains in its top a preferably toroidal light source 52 facing the photocell 50 to activate the photocell without interfering with the reciprocation of the needle during the sewing operation. The bobbin 'drive unit further comprises a main rotary spindle 54 connected to a slip ring assembly 56 serving the same purpose on the unit 22 which the assembly 36 serves on the needle drive unit 20. The main spindle 54 carries a gear 58 corresponding to gear 34, and coupled with the output gear 60 of a circumferential step motor 62 on'the mounting plate 28 of unit 22. The step motors 38 and 62 are driven in synchronism to cause the needle and bobbin drive units 20 and 22 to turn in unison around the needle axis with substantially zero lag between the units. The sine-cosine potentiometer 42 will also be turned in response to rotation of the output gear 40 of step motor 38.

- The movement of the two units 20 and 22 in unison along the right angular X and Y axes or combined movements parallel to these axes is accomplished through the operation of certain lead screws and driving step motors, asshown in FIGS. 2 through 5. In these figures, the machine is shown to embody a pair of spaced parallel support plates 64 and 66 constituting the basic support means of the machine. Various other support configurations may be utilized and the construction in the drawings is merely one possible arrangement. The two plates 64 and 66 are rigidly interconnected near their corners by posts 68 or the like. If preferred, the plates 64 and 66 can be independently supported from their top and bottom, respectively, thus completely eliminating any obstruction between the opposing units of the machine.

The plate 28 of needle drive unit 20 is clamped rigidly to a pair of parallel longiutdinally movable carriage bars 70, slidable in guide bearings 72 and also laterally shiftable with these bearings, as will be understood. At corresponding ends, the bars 70 are secured to a crosshead 14 having a nut 76 at its center, receiving a Y axis lead screw 78, journaled for rotation in fixed beraings 80 on the plate 64. The lead screw 78 is driven at the required times by a Y axis step motor 82 having a suitable driving connection with the lead screw. By this means, the needle drive unit 20 may be moved in either direction along or parallel to the X axis.

To allow movement of the unit 20 along or parallel to the x axis, a pair of stationary parallel guide bars 84 are mounted on the plate 64 through end supporting elements 86, and the guide bearings 72 for the bars 70 are slidable on the stationary bars 84 and move therealong in either direction. To effect this movement, a cross member 88 rigid with elements 72 is secured at its center to a push-and-pull bar 90 having a screw-threaded connection through a downturned extension 92 with an X axis lead screw 94, journaled for rotation in bearings 96, FIG. 4, on the plate 64, and having a driving connection with an X axis step motor 98 on the plate 64. To allow the necessary lateral movement of the elements 72 and 70 in the X axis direction along the guide bars 84, the nut 76 has a sliding connection with a guide bar 100, parallel to the X axis and carried by the crosshead 74. Conse quently, the needle drive unit 20 can be moved by the two right angular lead screws 78 and 94 in either the X axis or Y axis and in the plane which contains these two axes.

As best shown in FIG. 5, a substantially identical mechanism is provided on the other plate 66 for moving the bobbin drive unit 22 along the X and Y axes or parallel thereto. A very brief description of this duplicate X andn Y axis drive means for the unit 22 should suffice. The means comprises a Y axis lead screw 102 driven by a Y axis step motor 104 and connected through a nut 106 with a crosshead 108 having a bar 110 slidable through the nut 106 in the X axis direction. The crosshead 108 is secured to carriage bars 112, corresponding to the bars 70, and the bobbin drive unit 22 has its plate 28 rigidly clamped to the bars 112 for movement therewith in either direction along the Y axis, as dictated by lead screw 102.

An X axis lead screw 114 driven by an X axis step motor 116 on the plate 66 has a screw-threaded connection at 118, FIG. 4, with a push-and-pull bar 120, secured to a cross member 122, rigid with guide bearings 124 for the carriage bars 112. The guide bearings 124 are shiftable parallel to the X axis through sliding engagement with fixed parallel rails 126 on the plate 66, whereby the bobbin drive unit 22 like the needle drive unit 20 is rendered movable on both the X and Y axes in either direction.

As will be clearly understood from the description of the control circuitry, the two units and 22 are caused to move in unison in the X and Y axis directions and the two units may also be turning simultaneously on the Z axis or needle axis at this time. A variety of movements is possible and the sewing machine possesses great flexibility of operation. The two plates 64 and 66 are provided with large openings 128 to allow a full range of movement of the machine units 20 and 22 without interference.

Control circuitry Referring to FIGS. 7 through 9, FIG. 7 shows the control circuitry utilized for self-programmed operation of the sewing machine in the preferred embodiment thereof. In FIG. 7, the sine-cosine potentiometer 42 comprises a continuous circular resistance element 130 having a pair of terminals 132 and 134 coupled to the diametrically opposite halves of the resistance element. As indicated, a +12 volts is applied to the terminal 132 and 12 volts is applied to the terminal 134. Wiper arms 136 and 138 spaced 90 apart circumferentially are coupled to the shaft 140 of the potentiometer, FIG. 6, and are adapted to slide over the resistance element 130. This resistance element varies in value between the terminals 132 and 134 according to the sine of the angle of rotation of the potentiometer shaft 140, and therefore wiper elements 136 and 138 vary as the sine and cosine, respectively, of the angular position of the shaft 140. As already described, the shaft 146 is geared to the circumferential steps motor 38 of the needle drive unit 20.

The photoelectric cell 50, which turns and moves with the unit 20, feeds a voltage into a balanced bridge circuit 142, FIG. 7, which is coupled to two voltage-to-frequency converters 144 and 146. Circuitry embodying the voltage-to-frequency converters is disclosed at FIG. 4 of the mentioned application Ser. N0. 605,066. The outputs of voltage-to-frequency converters 144 and 146 are fed into respective one-shot multivibrators 148 and 150 which produce squarewave output voltage waveforms when triggered. The outputs of multivibrators 148 and 150 are coupled to logic level converters 152 and 154 by means of non-inverting buffer amplifiers 156 and 158.

FIG. 8 shows the circuitry embodying logic level converters 152 and 154 which circuitry comprises a first transsistor 160, adapted to be coupled to an input terminal 162 and to act as an inverter as well as an amplifier, while a second transistor 164 coupled to the collector of transistor 160, acts as an emitter-follower circuit to an output terminal 166. A 28-volt supply potential, when applied to a terminal 168 from a source not shown, provides a 28-volt squarewave output at terminal 166, for a 3.6-volt squarewave input at terminal 162. The outputs of the logic level converters 152 and 154 are coupled to motor controllers 170 and 172 which in turn are connected respectively to the circumferential driving step motors 62 and 38. The driving motors 62 and 38 are operated in a counterclockwise or clockwise direction depending upon the polarity of the output voltage of the balanced bridge 142, as described in application Ser. No. 605,066.

The photoelectric cell 50 is adapted to read the marginal edge of the cloth workpiece, such as a garment part, where a seam is to be stitched, or to read the edge of a cloth workpiece to be joined to another piece in a variety of sewing operations. The photocell programs the motor controllers 170 and 172 so as to cause step motors 62 and 38 to turn the units 22 annd 20 on the Z axis or needle axis, so that the needle or machine will faithfully follow the edge of the particular workpiece and the machine will thus head in a proper forward direction automatically. The machine units 20 and 22 ro tate around the needle axis to direct the machine along the workpiece edge, as a function of the voltage-to-frequency converter outputs, to step the circumferential drive motors 38 and 62 until such time as the bridge balance is re-established. This action is continuous as the photocell 50 reads or senses the margin of the workpiece.

Movement of the units 20 and 22 in the X and Y axis directions also takes place automatically as the machine follows the edge of the workpiece. The forward direction of the machine as established by the photocell and step motors 38 and 62 will determine the direction of movement, plus or minus, along the X and Y axes. This motion is implemented by the X and Y axis lead screws 94-114 and 78-102 and the associated step motors described in detail in connection with FIGS. 2 through 5. The sine-cosine potentiometer 42 being geared to circumferential step motor 38 of needle drive unit 20 provides a voltage proportional to the rotational angular position of the needle drive unit on the needle axis or Z axis. The photocell 50, being physically fixed to the unit 20, will scan in the direction established by the wiper arm 138 on the potentiometer 42. This constantly establishes what may be termed the forward direction of the machine. The output of the voltage-to-frequency converter 144, which is shaped and amplified in the multivibrator 148, provides pulse inputs to the logic level converter 152 for driving the circumferential step motors 38 and 62 in the clockwise direction. In like manner, the output of voltage-to-frequency converter 146, shaped and amplified in multivibrator 150, provides pulse inputs to the logic level converter 154 for driving step motors 38 and 62 counterclockwise. Regarding the voltage-tofrequency converters 144 and 146, essentially what happens is that the degree of unbalance of the bridge 142 generates a voltage which is transformed into a series of stepping pulses, the number of which pulses is proportional to the degree of bridge unbalance. Therefore, the motors 38 and 62 will be stepped in the proper direction sufficiently to re-establish bridge balance continually as the machine follows the edge of a workpiece or the like.

The X-Y axis control of the machine is implemented by operation of the respective pairs of step motors 98 and 116 and 82 and 104. The control is established in accordance with the positions of the wipers 136 and 138 of potentiometer 42. More specifically, the wiper arm 136 controls the X axis drive step motors 98 and 116 and the wiper arm 138 controls the Y axis drive step motors 82 and 104. The outputs of potentiometer 42 at the wiper arms 136 and 138 are simultaneously fed to a polarity converter 174, FIG. 7, and zero detectors 176 and 178. Zero detector 176 is coupled into the X axis control circuitry while zero detector 178 is in the Y axis control cricuitry.

The polarity converter 174 provides outputs for the X and Y axes, which are a full wave rectification of the input voltage applied thereto. The rectified outputs of the polarity converter 174 are coupled, respectively, to voltage-to-frequency converter 180 for the X axis control circuitry and to a voltage-to-frequency converter 182 for the Y axis circuitry. These voltage-to-frequency converters are similar to the converters 144 and 146 referred to above as being shown in detail in copending application Ser. No. 605,066. The outputs of the voltage-to-frequency converters 180 and 182 are proportional in frequency to the angular positions of wiper arms 136 and 138, respectively. For example, if the sewing machine is facing in a +X direction, then the frequency of the voltage-to-frequency converter 182 would be zero, be-

cause the voltage output from the sine-cosine potentiometer 42 would be zero, since the wiper arm 138 is midway between the +l2 volt and -12 volt potentials applied to terminals 132 and 134. Likewise, there will be no movement of the machine along the X axis if the machine is facing in a Y axis direction because the wiper arm 136 of the potentiometer will then be at the zero voltage position. If the position of the machine at any given instant is somewhere in between the extreme X and Y axis positions, then there will be a proportional movement of the machine parallel to both axes, dependent upon the positions of the wiper arms 136 and 138.

The outputs of voltage-to-frequency converters 180 and 182 are coupled, respectively, into NOR gates 184 and 186. A second input is applied to both NOR gates 184 and 186 from a Schmitt trigger circuit 188 which is comprised of NOR circuits 190, 192 and 194, which are coupled together in a well-known manner to provide a circuit which is amplitude-sensitive. This produces a well defined squarewave output of selective magnitude whenever the threshold voltage thereof is exceeded. The input to the Schmitt trigger circuit 188 is comprised of the output from a rotary transducer 196 which is coupled to the needle drive shaft of a machine unit 20. The rotary transducer 196 provides an electrical output signal during the time that the needle 46 is in the workpiece. The rotary transducer 196 output is then shaped in the Schmitt trigger circuit and applied to the NOR circuits 184 and 186 to prevent the X and Y axis step motors 98116 and 82-104, respectively, from being moved while the needle 46 is penetrating the cloth or workpiece.

The output from the NOR circuit 184 is coupled to a plus and minus switch 198 comprised of interconnected NOR gates 200 and 202. One input to the NOR gates 200 and 202 consists of the output from an inverting butfer amplifier 204. The other input to the NOR gates 200 and 202 is applied from the X axis zero detector 176, comprising three interconnected NOR gates 206, 208 and 210. The output from potentiometer wiper arm 136 is coupled to the zero detector 176 in such a manner that a common input is supplied to NOR gates 206 and 210. The output from NOR gate 208 is coupled to the aforementioned input to NOR gate 202, while the output of NOR gate 210 is coupled to the input to NOR gate 200. The plus and minus switch 198 determines the direction of movement or along the X axis, FIG. 1.

Similarly, a second plus and minus switch 212 comprising NOR gates 214 and 216 is coupled to the NOR gate 186 through an inverting buffer amplifier 218 and the zero detector 178, which is comprised of interconnected NOR gates 220, 222 and 224. The input to zero detector 178 applied to NOR gates 220 and 224 comes from wiper arm 138 of sine-cosine potentiometer 42. The plus and minus switch 212 determines the direction of movement of the sewing machine or along the Y axis. Both zero detectors 176 and 178 include a pair of diodes 226 and 228 coupled in series from the input to the NOR gates 206 and 220, to ground, for bypassing any positive potential appearing thereat to ground.

The plus and minus switches 198 and 212 are controlled by their respective zero detectors 176 and 178, by detecting the zero crossover point of wiper arms 136 and 138 each time the sine-cosine potentiometer 42 passes through a zero voltage level. For example, if the wiper arm 136 passes through a zero crossover point in one direction, an output will appear at either of the NOR gates 208 or 210, which are coupled to the respective NOR gates 202 and 200 in the plus and minus switch 198. The outputs appearing at either NOR gates 202 and 200 are then applied to logic level converters 230 and 232, after passing through inverter buffer amplifiers 231 and 233. The logic level converters 230 and 232 are shown in detail in FIG. 9.

Referring to FIG. 9, the logic level converters are comprised of two transistors 234 and 236, coupled together as an amplifier stage and an emitter-follower. The input to the amplifier stage comprising transistor 234 is applied to the base thereof by means of a capacitor 238 coupled between input terminal 240 and the base of transistor 234. The collector of transistor 234 is directly connected to the base of transistor 236 and the output is coupled from the emitter thereof to an output terminal 242. A 6 volt supply potential is applied to a terminal 244 which is 8 coupled to the respective collectors of transistors 234 and 236, due to the fact that these are PNP transistors. An input having a 0 to 3.6 volt amplitude is inverted to provide an output having an amplitude varying between 0 and -6 volts.

The output of logic level converter 230 is commonly coupled to one input of motor controllers 246 and 248 while the output from the logic level converter 232 is commonly coupled to the other input of the motor controllers 246 and 248.

An output from logic level converter 230 produces a signal causing motor controllers 246 and 248 to drive both X axis drive step motors 98 and 116 in one direction; while an output from the logic level converter 232 produces another signal causing motor controllers 246 and 248 to drive both X axis drive step motors 98 and 116 in and opposite direction.

Considering now the Y axis control of the machine, the zero detector 178 will provide an output at one of the NOR gates 222 or 224 depending upon the crossover direction, to provide an output from the plus and minus switch 212 at either of thet NOR gates 214 or 216. The outputs appearing at either of the NOR gates 214 or 216, after passing through inverter buflfer amplifiers 250 and 252, are then applied to logic level converters 254 and 256, identical to the logic level converters 230 and 232, the latter having been shown and described in detail in connection with FIG. 9. The output of logic level converter 254 commonly is coupled to Y axis motor controllers 258 and 260 which drive Y axis step motors 82 and 104 in one direction. The logic level converter 256 is commonly coupled to the other input of motor controllers 258 and 260, which drive Y axis step motors 82 and 104 in the opposite direction. Thus, the Y axis drive is identical to the above-described X axis drive and the X and Y axis step motors for the machine units 20 and 22 are always operated in pairs by the circuitry.

In summation, the self-programmed circuitry in FIG. 7 incorporates a photoelectric sensing cell which drives or leads the two circumferential drive motors 38 and 62 in a stepping mode so as to keep the needle and bobbin drive units 20 and 22 synchronized and facing in a direction to follow the edge of the workpiece. Information proportional to the angular position of the units 20 and 22 on the needle axis is taken from the sine-cosine potentiometer 42 and fed through the described logic circuits to operate the X and Y axis step motors 98 and 116 and 82 and 104 in either the positive or negative direction, as determined by zero detectors 176 and 178. This causes the two machine units 20 and 22 to always synchronized and to always head in the proper direction and to always move in the proper direction along the X and Y axes.

Machine operation under external control When it is desired to operate the sewing machine under external control, by a tape reader or some similar input device, instead of in a self-programmed mode, a servo system such as the one shown in FIG. 10 is utilized. In FIG. 10, two servo amplifiers 262 and 264 are coupled to and drive two serve drive motors 98 and 116 which are the X axis drive step motors previously described in connection with the self-programmed machine.

Power for the servo system is obtained from a 115- volt -cycle potential, FIG. 10, applied to a terminal 266 from a suitable source, not shown. This supply potential is applied through a main power switch 268 and fuse 270 to a DC power supply 272 which is adapted to to provide a 28-volt DC potential to a terminal 274. An auxiliary terminal 276 is also provided for having a fused ll5-volt 60 cycle supply voltage available. A volt 400-cycle supply shown at 278 is coupled to the DC power supply 272 and provides a 400-cycle output at a terminal 280. A switch 282 which may be, for example, switch contacts under control of a conventional tape reader is coupled to the terminal 274 which, when closed, applies a 28-volt potential across the potentiometer 284.

A voltage level proportional to the setting of potentiometer 284 is applied to the input of servo amplifier 262. The rise time of the input voltage, however, is delayed approximately one second by the time constant of the coupling network comprising a resistor 286 and a capacitor 288. This provides for a gradual acceleration of servo drive motor 98 from rest to running speed determined by the position of potentiometer 284.

When the voltage is sensed at the input of servo amplifier 262, a drive voltage to the X servo drive step motor 98 is produced, which in turn drives shaft 290 to a gear train comprising gears 292, 294 and 296. A tachometer generator 298 is coupled to the gear 294 and generates a negative voltage proportional to the speed of servo drive motor 98, which is fed back to the input of servo amplifier 262 to provide speed regulation.

A synchro-control transmitter 300 is coupled to the gear 296 and the stator windings, not shown, are couplied to the stator windings of a synchro-control transformer 302, which is coupled to a gear 304 forming a part of a gear train additionally having gears 306 and 308. A 400- cycle reference voltage is applied to the rotor windings of the synchro-control transmitter 300 from the power supply 278, and a read-out appears on the stator windings proportional to the angular displacement of its rotor shaft. When this angular information is supplied to the control transformer 302, an error voltage appears on the rotor windings, not shown, which is proportional to the angular displacement of the control transformer rotor shaft. This error signal is applied to the input of servo amplifier 264 through the variable resistance 310. When the error voltage appears at the input of servo amplifier 264, a drive voltage is applied to the servo drive motor 116, which produces a rotation in any direction which drives the rotor of control transformer 302 to a null position through gear train comprising gears 308, 306 and 304.

This change in angular position is in the direction to follow the motion of servo drive motor 98, and will continue to change until the error signal is reduced to zero or substantially Zero. Shaft 312 coupled to gear 306 is then made to follow the angular displacement of shaft 290. A tachometer 314 provides a negative feedback voltage to servo amplifier 264 for providing stability. Additionally, tachometer 298 supplies an input to servo amplifier 264 through a variable resistor 316 for improving the tracking ability at high speed operation. This input is proportional to speed, and gives the shaft 312 a small additional boost as speed increases to reduce the angular error between the two shafts 290 and 312 to the absolute minimum.

In summation, the system shown in FIG. electronically links the physically separated needle drive and bobbin drive units 20 and 22 for operation in unison. As long as switch 282 remains closed, the servo drive motor 98 will turn, causing the servo drive motor 116 to follow with substantially zero lag or error. Upon opening the switch 282, all operations stop and both servo drive motors 98 and 116 immediately come to a halt. It can readily be understood that the servo system shown in FIG. 10 is merely duplicated for the Y axis drive utilizing servo drive step motors 82 and 104 in the same manner that the servo motors 98 and 116 are used in the X axis drive system. The system is similarly constructed for controlling rotation of the machine units 20 and 22 around the needle axis or Z axis. Therefore, a remote control system is achieved for operating the sewing machine without a human operator but under external control rather than in a self-programmed mode.

Work supporting and feeding The nature of the work supporting and/or feeding means employed will vary depending upon the class of work being performed by the machine. In general, the work will break down into approximately five categories 10 and FIGS. 11 through 16 of the drawings illustrate some what diagrammatically the different classes of work and the types of work supporting and feed means which are utilized under the different circumstances.

Because of the rather wide variation in the work supporting and feed means, this means has been omitted in FIGS. 1 through 6 of the drawings to avoid confusion and it will be understood that the basic sewing machine structure involving needle drive unit 20 and bobbin drive unit 22 remains unchanged and operates in the same manner regardless of the type of work being performed. Therefore, in connection with FIGS. 1 through 6, it should be understood that any of the work support and feed means shown in FIGS. 11 through 15 may be utilized with complete success and additional means, not shown in the application, can be devised for use with the basic sewing machine units 20 and 22. In each of FIGS. 11 through 16, the needle drive and bobbin drive units 20 and 22 are shown in their relation to the work and supporting and/or feed means, and a clear understanding of the operation of the machine with respect to different classes of work can be gained from a consideration of these drawing figures, taken in light of the foregoing detailed description of the machine which essentially consists of the two units 20 and 22 and their electronic controls.

The first type of operation performed by the machine involves joining relatively large fiat parts along matched edges 318, which edges may be irregular as shown in FIG. 11. This type of work includes seaming pants fronts, backs and sides and goring skirts and the like. Referring to FIG. 11, the needle drive and bobbin drive units 20 and 22 are operated in the manner previously described. The cloth workpiece 320 consists of two plies of cloth matched for joining along the irregular edge 318. The workpiece 320 in this embodiment is constantly supported from below during all movements of the sewing machine by a lower plate 322 attached to bobbin drive unit 22 and movable therewith on all axes. There is also a relatively stationary upper plate 324 which may slidably engage the lower plate 322 but does not move therewith. The sewing machine including units 20 and 22 moves relative to the plate 324. The thicknesses of the two plates has been exaggerated in FIG. 11 for clarity.

Air jets 326 are directed upwardly at an angle against the bottom of the workpiece 320 to maintain a slight tension toward the edge 318 and to maintain the workpiece fiat in the immediate vicinity of the needle 46 which still permitting the lower plate 322 to move beneath the workpiece.

Upper and lower belts 328 and 330 grip the workpiece 320 and move it into the sewing area which is the area within which the machine units 20 and 22 are capable of movement. The belts and workpiece are then brought to rest at the sewing area and the sewing machine will follow the contoured edge 318 and produce the desired line of stitching 332 along this edge joining with two plies of material which constitute the workpiece 320. As fully described, the sewing machine will automatically make the necessary movements on both an X and Y axes as well as rotational movement on the Z axis or needle axis.

A clearance opening 334 in the stationary plate 324 indicates the width or size of the opening required where the sewing machine moves only on the X axis as the belts 328 and 330 or other feed means move the cloth on the Y axis. Here again, the flexibility of the sewing machine is very apparent. The machine may in some instances be equipped with more-or-less conventional feed dogs or other types of overhead feed means may be employed.

Another possibility, not shown in the drawings, is that cloth workpieces may be sewed to a paper support or belt, and other the sewing operation, the paper can be stripped away automatically. This operation is practical particularly since seams do not ordinarily extend completely around the marginal edge of the workpiece. The arrangement shown in FIGS. 11 and 11a will be employed in a large number of applications although by no means in all cases.

FIG. 12 relates to another class of work where the object is to stitch around, usually partially around, small individual pieces for joining them together, such as in the making of collars and cuffs from several small matched plies of material. Referring to FIG. 12, a horizontal conveyor belt 336 moving in the direction of the arrow carries work clamps 338 toward the sewing station where the sewing machine 20 is indicated. The clamp 338 is open at the first position A, ready for loading, and ready to receive a three-ply collar 340. At position B, the clamp 338 is loadedand closed and the collar 340 is moving toward the sewing position C. At the sewing position C, the belt 336 and clamp are halted and the electronic sewing machine produces the line of stitching 342 partly around the margin of the collar, while the machine is in a self-programmed mode. Finally, at position D, the work has been moved beyond the sewing area and clamp 338 has reopened and the completed collar is ready for removal and stacking.

FIGS. 13 and 13a show a variation of the procedure for making collars and the like. In these figures, cloth 334 is drawn in the required number of plies from supply rolls 346, 348 and 350. All plies pass through tensioning rolls 352 and are advanced stepby-step by feed rolls 354. The scrap is wound up at 356. FIG. 13 shows the sewing machine operating in a self-programmed mode to produce the collar-forming lines of stitching 358 in the several plies of cloth each time the cloth advances a step and halts at the sewing area. At a position E, the cloth 344 is cut by die apparatus, not shown, outside of the stitching lines 358. This produces a finished collar which may be turned right side out and removed and stacked. The remaining scrap is rolled up at 356.

Referring to FIG. 14, another work operation involves stitching around, or partially around, small parts such as appliques or pockets which are to be sewed to larger parts. In FIG. 14, the sewing machine is indicated at the sewing station in a self-programmed mode for sewing a pocket part 360 to a larger section 362, which is a section of a coat or the like. At a first position F, parts 360 and 362 are placed on a lower belt 364 in superposed relation for movement to the sewing position G. An upper belt 366 engages the work at this area and the sewing machine produces the required stitching 368 around the pocket. The completed work is then moved to position H beyond the sewing area for appropriate disposal.

FIG. 15 pertains to operations where it is required to sew long seams joining large parts, such as parts of tents or joining two large rolls of material transversely. In these operations in particular, the limited throat of conventional machines is troublesome. The invention machine is ideally suited to these operations because the throat depth is infinite, in that there is no mechanical linkage between the units 20 and 22 but only an electrical connection. In FIG. 15, large cloth rolls 370 and 372 are illustrated and are to be joined transversely by long lines of stitching 374 which the sewing machine is capable of producing. The machine units 20 and 22 in such an application are suitably mounted on upper and lower support tracks 376 and 378 which can easily span several yards and are equipped with a suitable linear drive for the machine, which will move in the direction of the arrow.

Operations are contemplated with the machine units 20 and 22 for joining parts of garments along compound three dimensional curves as occur at the shoulders of shirts, coats and the like. Referring to FIG. 16, by mounting the machine units 20 and 22 inside of supporting rings 380 and 382 (or half rings) with their axes at right angles, rotation of the sewing machine around the three X, Y and X axes is attainable, as shown by the arrows.

Also, the machine may be moved as required along any or all of the X, Y and Z axes selectively. The combining of these movements will allow the machine to sew along any compound curve on a three dimensional form.

It is to be understood that the forms of the invention herewith shown and described are to be taken as preferred examples of the same, and that various changes in the shape, size and arrangement of parts may be resorted to, without departing from the spirit of the invention.

What is claimed is:

1. A sewing machine comprising physically separated needle and bobbin drive units which cooperate to produce stitching in a workpiece, and means electrically coupling said drive units and enabling them to operate substantially in unison and to move together in prescribed directions while free of physical connection, said means including mechanism for shifting both drive units in unison in opposite directions along X and Y axes and for turning both drive units in unison on the needle axis of the sewing machine.

2. A sewing machine as defined by claim 1, and remote programming tape reader means coupled with the firstnamed means.

3. A sewing machine as defined by claim 1, and wherein said X and Y axes lie in one plane relative to said units and the needle axis of the machine is in a plane substantially perpendicular to the first-named plane.

4. A sewing machine as defined by claim '1, and wherein said mechanism comprises plural synchronized motor drives for shifting both machine drive units in unison along said X and Y axes, and additional synchronized motor drives for turning said machine units in unison upon the needle axis of the machine.

5. A sewing machine as defined by claim 4, and wherein said plural motor drives comprise synchronized pairs of X and Y axis step motor drives for said needle and bobbin drive units, said pairs driving said units substantially in right angular directions, and said addtional synchronized motor drives comprising synchronized circumferential step motors and gearing connected with each of said units for turning them in unison on said needle axis.

6. A sewing machine as defined by claim 5, and a rotary electrical slip ring assembly connected with said gearing for each of said units.

7. A sewing machine as defined by claim 5, and wherein each X and Y axis step motor drive includes a rotary lead screw, and a carriage means for each of said sewing machine drive units and the carriage means of each unit having a connection with a right angular pair of said lead screws so that the unit may be accurately moved in opposite directions along said X and Y axes.

8. A sewing machine as defined by claim 6, and a rotary potentiometer means connected with and operated by the gearing of one of said units.

9. A sewing machine as defined by claim 7, and wherein said machine drive units are mounted on coaxial bearings on the needle axis of the machine for ease of turning under influence of the circumferential step motors and gearing.

10. A sewing machine as defined by claim 8, and electronic control circuitry including logic circuitry connected with the potentiometer and also connected with said X and Y axis and needle axis motor drives.

11. A sewing machine as defined by claim 7, and a supporting structure for the sewing machine including guide rail means for said carriage means.

12. A sewing machine as defined by claim 10, and an electrical sensing element on at least one of said machine drive units and having a connection within said control circuitry and being capable of establishing a forward direction of the machine with respect .to its needle axis, whereby the sewing machine may be programmed to follow the edge contour of a workpiece.

13; A sewing machine as defined by claim 12, and wherein said sensing element is a photoelectric cell.

14. A sewing machine as defined by claim 13, and wherein said photoelectric cell is mounted on said needle drive unit close to said needle and a coacting source of light on the bobbin drive unit, said cell and light source lying on opposite sides of a workpiece in the sewing zone of the machine.

15. A sewing machine comprising a needle drive unit, means supporting the needle drive unit for movement along substantially right angular axes in one plane and for turning movement on the needle axis, said needle axis being substantially at right angles to said plane, drive means for the needle drive unit along said right angular axes and around said needle axis, a bobbin drive unit in spaced opposed relation to the needle drive unit and being entirely free of mechanical connection therewith, means supporting the bobbin drive unit for movement along substantially right angular axes in a plane spaced from and parallel to the first-named plane and for turning movement on said needle axis, and drive means for the bobbin drive unit along the second-named right angular axes and around said needle axis, the first and second-named drive means being synchronized whereby the needle and bobbin drive units will move substantially in unison along said right angular axes and around said needle axis.

16. A sewing machine as defined by claim 15, and wherein each of said drive means comprises a separate motor drive for each unit along said right angular axes and around said needle axis, the separate motor drives of the needle drive unit and bobbin drive unit being synchronized.

17. A sewing machine as defined by claim 16, and wherein said separate motor drives each includes a step motor, electronic control circuitry for the step motor, and means forming a driving connection between each step motor and one of said units.

18. A sewing machine as defined by claim 15, and electronic circuitry interconnecting and controlling the operations and synchronization of the first and second-named drive means.

19. A sewing machine as defined by claim 18, and wherein said control circuitry includes a photoelectric scanning means on one of said units, and a responsive rotary potentiometer on said unit and turned when said unit is caused to turn by its drive means around said needle axis.

20. A sewing machine comprising physically separated needle and bobbin drive units which cooperate to produce stitching in a workpiece, supporting and guiding means for said drive units enabling them to move in prescribed directions in substantially parallel planes and to revolve around a common axis substantially normal to said planes, and electrical coupling means for said needle and bobbin drive units causing them to move in unison in said planes and around said axis while said units remain free of physical connection.

References Cited UNITED STATES PATENTS 2,059,845 11/1936 Bowersox 112-117 2,690,724 10/1954 Eisenbeiss 112-220 XR 2,797,656 7/1957 Reid 112-2 3,072,081 1/1963 Milligan et al 112-2 3,204,590 9/1965 Rockerath et al. 112-203 XR 3,329,109 7/1967 Portnoff et a1. 112-102 XR 3,354,850 11/1967 Story 112-79 XR 3,385,244 5/1968 Ramsey et a1. 112-102 XR 3,385,245 5/1968 Ramsey et a1. 112-102 XR FOREIGN PATENTS 1,037,853 5/1953 France. 1,158,800 12/1963 Germany.

JAMES R. BOLER, Primary Examiner US. Cl. X,R. 112-102, 220 

